The overall objective is to investigate the metabolism of retinol and retinoic acid in the rat. The objectives for the current year are (1) to determine the half-life and "metabolism time" of retinol in control rats which had received retinyl acetate supplements; (2) to characterize the urinary metabolites of retinol and retinoic acid in an attempt to provide a specific method for detection of vitamin A deficiency in animals and humans; and (3) to determine the levels of retinol and its metabolites in rat and human tumors with a view to inquire the relationship of vitamin A to chemical carcinogenesis.